The Eye and How It Works pt 1 Flashcards
What is the name of the opening between the upper and lower eyelids?
palpebral fissure
What is the name of the muscle that lifts open the upper eye lid?
levator palpebrae superiors
What is the thick layer of connective tissue that protects the eye and is located in the upper eye lid?
tarsus
What is the function of the eyelid?
protects the eye from injury and spreads tears over the eye
What is the triangular space on the sides of the cornea when the eyes are open called?
canthi - lateral canthus (outside of eye) and medial canthus (inside of eye)
Purpose of eyelids (2)
Protect the eye from injury and excessive light
The inside corner of the eye where eye boogers are found. It is modified skin that contains sweat and oil glands with fine cilia.
caruncle
Round muscle that goes all the way around the eye that helps the eye close.
orbicularis oculi
Three places where tears are formed
lacrimal gland, goblet cells, meibomian glands
Small hole near the caruncle that drains tears
punctum
small tube between punctum and lacrimal sac
canaliculi (canaliculus - plural)
Three functions of tears
forms a smooth refractive surface on the corneal epithelium, maintains a moist environment for the corneal epithelium, carries oxygen to the cornea
Tear Flow (3)
punctum -> canaliculus -> lacrimal sac
The opaque “white” of the eye.
sclera
What is sclera made of?
connective tissue - makes the eye strong to prevent penetration and protect the eye. It also allows passage of nerves and blood.
Where the optic nerve goes through the sclera.
lamina cribrosa
Part of sclera that is the vascular section. It has connective and elastic tissue to allow the eye to have some give and movement.
episclera
mucous membrane that covers the sclera. It is very thin like saran wrap and is continuous from the eyeball to the lid.
conjunctiva
2 parts of the conjunctiva
palpebral (on the lids itself) and the bulbar (on the eyeball)
Purpose of the conjunctiva
defend and repair the cornea from scratches, wounds and infections.
Catches microorganisms
The junctional bay created when the two portions of the conjunctiva meet
fornix
What is the conjunctiva made up of?
secretory elements from blood vessels (nutrients, antibodies & leukocytes)
cellular- secretes mucous and oil
Transparent, clear, shiny area at the front of the eye.
cornea
Details about cornea (3)
- fully developed by age 2
- thickness is maintained
- convex
The 1mm transitional zone between cornea and conjunctiva
limbus
5 layers of the cornea
epithelium
Bowman’s layer
stroma
Descemet’s membrane
endothelium
Epithelium (4)
-Outer part of the cornea (touches tears)
-5-7 cells thick (50 microns)
- barrier and refractive surface
- rapid regeneration without scarring
Bowman’s Layer (2)
-acellular
-10 microns thick
Stroma (2)
-Thickest layer of cornea (makes up 90% of the corneal thickness)
- 78% water
Descemet’s Membrane (2)
-3-12 microns thick
-basement membrane (attaches to something)
Endothelim (2)
-4-6 microns thick
-500,000 cells that you are born with
What provides nourishment to cornea (3)
- plexus of fine capillaries at limbus
- tear film
- Aqueous humor (clear fluid between cornea and iris)
**there are NO blood vessels in cornea
Uvea (3)
iris, cilliary body, choroid
**High blood vessel/blood flow area
very outermost part of uvea
iris
Iris (4)
- very outermost part of uvea
- central circular aperature (pupil)
- many ridges and furrows
- 2 muscles (sphincter - closes, dialator - opens)
Ciliary Body
-behind iris
- connected to sclera
- cilliary processes (plump with many folds, 2/5 mm thick, products aqueous humor)
- zonular fibers (fine ligamentous fibers that attach to lens)
what connects to cilliary body to control shape of lens
zonular fibers
What lies between the retina and sclera that is a vascular structure that provides nourishment to retina?
choroid
Structures of “the angle” (5)
- root of iris
- anterior surface of ciliary body
- scleral spur
- canal of Schlemm
- trabecular meshwork
4 steps of “the angle”
*aqueous hum0r through trabecular meshwork
- trabecular meshwork contains pores that takes the aqueous to schlemm’s canal
- aqueous then leaves the eye through aqueous veins that penetrate the sclera
*Obstruction leads to glaucoma
lens shape
biconvex (front and back bow outward)
lens diameter
9-10 mm (about 1 cm)
lens equator
attachment for zonular fibers
lens capsule
transparent, elastic envelope that hardens with age
lens nucleus (2)
-develops in our 30s
-The central portion of the len
lens cortex
outer lens fibers
The lens onion effect
The lens keeps growing until it gets too big. The center grows outward and we never lose a cell This happens in our 40s and prevents us from being able to focus on close up objects.
What makes up 2/3 of the interior volume of the eye?
vitreous humor
what is vitreous humor
99% water - jelly like substance, thick and viscous
What is vitreous humor made up of?
matrix of collagen fibers
hyaluronic acid
This is anchors at the ora serrata, optic nerve and various points on the retina
vitreous humor
the serrated junction between the retina and the ciliary body
ora serrata
What causes floaters in the eye?
The collagen fibers in the vitreous humor break away, condense and lose transparency
This part of the eye is an extension of the brain
retina
How many layers does the retina have?
10
This photoreceptor is responsible for seeing in dim light, is often associated with poor vision as well as action vision and there are about 125,000,000 of them.
rods
This photoreceptor is responsible for color vision, fine detailed vision and there are about 6,000,000 of them.
cones
The part of the retina where all fine detail comes from
central
This part of the retina has a concentrated area of cones and damage to it dramatically reduces acuity.
macula lutea (central)
This part of the retina is where most of the rods are located and damage to it causes night blindness
peripheral
This sends nutrients to the retina and attaches to the choroid
pigment epithelium
The part of the eye at the posterior of the globe that sends visual impulses from the retina to the brain. It has 1,000,000 axons.
optic nerve
This supplies 1/3 of blood to the eye and has arteries and veins that branch in an arc patterns
optic nerve
Where does optic nerve enter globe?
through the sclera in the lamina cribrosa (the basement of the physiological cup)
This keeps what each eye sees on the left side together and what each eye sees on the ride side together.
optic chiasm
Where the nasal fibers of one eye have joined with the temporal fibers of the other.
optic tract (the portion after the optic chiasm after the crossover happens)
The relay station where fibers spread out in a fan shaped manner and extend to the parietal and temporal lobes.
Lateral Geniculate Body
The area of the occipital lobe where conscious recognition occurs.
visual striate area
the six muscles that move the eyeball
superior oblique
inferior oblique
superior rectus
inferior rectus
medial rectus
lateral rectus
This muscle adducts the eye to move it horizontally towards the nose
medial rectus
This muscle abducts the eye to move it horizontally to the outside
lateral rectus
This muscle moves the eye up
superior rectus
This muscle moves the eye down
inferior rectus
This muscle causes intorsion, moving the eye up and inward
superior oblique
This muscle causes extorsion, moving the eye away from and down from the nose
inferior oblique
